1. Field of the Invention
This invention relates to a distributor for an internal combustion engine, and more particularly to a distributor for an internal combustion engine which includes means for reducing noise radio waves caused by discharge sparks upon the distributing operation. The invention further relates to a method of producing a rotor electrode of such distributor.
2. Description of the Prior Art
A conventional distributor for an internal combustion engine includes a rotor electrode provided on a distributor rotor secured to a rotary shaft which is rotated in a synchronized relationship by rotation of a crankshaft of an internal combustion engine. A plurality of side electrodes are disposed along a locus of rotation of the distributor electrode with a discharge gap left therebetween. A contact element is resiliently pressed against and contacted with an upper face of the distributor electrode and connected to ignition coils by way of a lead wire.
During rotation of the distributor rotor, each time the distributor electrode approaches a side electrode, a high voltage is applied between the electrodes to cause discharge in the discharge gap defined between the electrodes so that the high voltage is distributed successively to the ignition plugs of cylinders of the engine. In this instance, noise radio waves are produced by a spark discharge which takes place in the discharge gap between the distributor electrode and the side electrodes. Those noise radio waves make radio faults to radio broadcasting, television broadcasting, various radio communication devices and electronic devices and deteriorate the S/N ratio of those devices.
Various means have been proposed for reducing production of such noise radio waves. An exemplary one of such means is disclosed, for example, in Japanese Patent Publication No. 51-38853. The means includes a layer of a high resistance substances formed at a location of a surface of a distributor electrode adjacent side electrodes of a distributor. The presence of such high resistance substance layer is effective to reduce the electric field strength of noise radio waves produced upon discharging between the distributor electrode and a side electrode.
However, the conventional distributor for an internal combustion engine having such a construction as described above still has the following drawbacks. In particular, while the high resistance substance layer on the distributor electrode exhibits a significant effect upon measurement of noise radio waves in accordance with peak detection (SAE Standards) which is one of measurements when classified depending upon a detecting method, it does not exhibit a sufficient effect upon measurement in accordance with quasi-peak detection (CISPR Standards). Consequently, an effect of noise radio waves particularly upon an FM radio is not solved as yet. Besides, the insulator layer on the distributor electrode makes the discharge unstable and increases radio noises.